The development and maintenance of connections between motor neurons and muscle are critical to normal physiological function. Nowhere is the result of disrupting these connections more devastating than in patients with degenerative motor neurons diseases such as amyotrophic lateral sclerosis (ALS). During ALS many motor neurons die, leaving the muscles without ability to function. Little is known about why they die. During development there is a period of normal cell death for many neurons including motor neurons; however not all the neurons die as they do in ALS. What are the mechanisms that regulate and restrict this cell death? Coincident with this period of cell death is a period of rapid induction of proteins required for normal motor neurons function such as choline acetyltransferase (ChAT). Do the same molecules that regulate cell death also regulate the differentiation of the surviving neurons? Could these mechanisms be disrupted in ALS? the objectives of this study are to isolate molecules that may be involved in regulating motor neuron death and development, and to understand the molecular mechanisms by which they act. These objectives will be accomplished by using cultures of pure motor neurons form the chick ciliary ganglion (CG) as a bioassay for trophic molecules. Our previous work has identified two distinct biological activities that affect the development of CG neurons: ChAT- stimulating activity (CSA) and growth promoting activity (GPA). CSA stimulate specific induction of ChAT, which is essential for functional neural transmission, and GPA supports survival and long-term growth of CG neurons. The specific aims of this proposal are: 1. To purify the molecules responsible for GPA and CSA and to obtain sufficient amino acid sequence information to clone their cDNAs; 2. To raise monoclonal antibodies against GPA and CSA by utilizing partially purified fractions of the activities; and 3. To test the specificity of action of GPA and CSA on other neuronal cell types. Future work will involve using the purified molecules and the antibodies obtained in this study to test the hypothesis that survival, growth and differentiation of motor neurons are controlled by the GPA and CSA released by neuronal target tissues such as muscle.